Control circuitry for controlling a spa water heater, wherein a microcontroller is configured to detect zero crossings of an A.C. line voltage from a voltage sense signal, to cause closing of a first heater relay and a second heater relay, to detect the time at which heater current is initially sensed by a current sensor after the initial closing of the second heater relay, to measure a time delay between the time that the second heater relay is closed and the time at which heater current is initially sensed, and to adjust the time at which a second closing of the second heater relay occurs such that zero crossings of the heater current occur at the same time as zero crossings of the voltage waveform. The control circuitry further includes a voltage sense circuit comprising a first diode connected in series with a current limiting resistance connected in series with a Zener diode, which is in turn connected in series with an optical coupler LED.

According to an embodiment, a status estimation apparatus includes detector, calculator, estimator and specifying unit. Detector detects a status change of any of electrical devices based on measurement data of a current flowing in a distribution line supplies power to the devices. Calculator calculates a current waveform change and a power change associated with the status change based on the measurement data. Estimator estimates a candidate originating from the status change based on the current waveform change. Specifying unit specifies a device caused the status change and a type of the status change based on the power change and an estimation result of the candidate.

A method for evaluating signal attenuation of an impedance member includes setting at least one ideal attenuation of an ideal impedance member, setting at least one attenuation range for the at least one ideal attenuation, measuring at least one first test attenuation at a first test signal frequency of the subject impedance member, measuring at least one second test attenuation at a second test signal frequency of the subject impedance member, comparing the at least one first test attenuation and the at least one second test attenuation with the at least one attenuation range for the at least one ideal attenuation, determining whether the at least one first test attenuation and the at least one second test attenuation fall within the at least one attenuation range and performing a troubleshooting function on the subject impedance member if the at least one first test attenuation or the at least one second test attenuation fall outside the at least one attenuation range.

A shunt-based current sensor executes redundancy detection of a load current flowing through a load by using a shunt resistor. The shunt-based current sensor includes a reference resistor, a current excitation circuit, at least two voltage measurement circuits and a signal processing circuit. The reference resistor is connected to the shunt resistor in series. The current excitation circuit generates an AC excitation current and supply the AC excitation current to the shunt resistor and the reference resistor. At least two voltage measurement circuits measure a voltage across the shunt resistor. A signal processing circuit executes signal processing based on respective measurement voltages of the at least two voltage measurement circuits, and is operated in the load current redundancy detection mode or a shunt resistance measurement mode.

A tracking current is separated easily. A current measurement apparatus 10 according to the present disclosure is configured to measure a tracking current. The current measurement apparatus 10 includes a magnetic core 11 that can be disposed so as to enclose wiring 100 to be measured, and first and second coils L1 and L2 wound on the magnetic core 11. The number of turns of the second coil L2 is smaller than that of the first coil L1. The second coil L2 is configured to be able to detect the tracking current flowing through the wiring 100.

The present invention is directed to an RFID device. The RFID device includes a brace affixed to an inductor or capacitor. The brace is constructed from a material structurally responsive to a predetermined stimulus, such that stimulus-responsive structural alterations to the brace structurally alters the inductor, capacitor, or other RFID subcomponent of the RFID circuit capable of generating a current alteration, which in turn alters the signal frequency of the RFID.

Various aspects provide a high frequency voltage supply monitor capable of monitoring high frequency variations of the voltage supply inside a microelectronic circuit substantially in real time. The voltage supply monitor can comprise a differential amplifier circuit having a substantially constant gain over a wide bandwidth, allowing the supply voltage variations to be amplified according to a known gain under a wide range of conditions. The amplified signal can then be sent to an output port for monitoring and measurement by an external display device.

A method of measuring current for fault detection in a distribution grid. The method includes: using three current transformers, wherein three current transformers are connected to one another; installing three connected current transformers in series on three phase conductors by winding; measuring voltages of three series connected current transformers by measuring first voltage over first current transformer, measuring second voltage over first current transformer and second current transformer, measuring third voltage over first current transformer, second current transformer and third current transformer; using measured first voltage, second voltage and third voltage for determining sum current; using measured first voltage, second voltage, third voltage and calculated sum current for calculating phase currents; using determined sum current and phase currents to detect first fault transient in the distribution grid.

A process for current measurement includes a recombination of a low frequency current signal ILF coming from a low frequency current sensor and at least one high-frequency current signal IHF+offset coming from a high-frequency sensor on a single current conductor. The process includes the steps of amplification, filtering, and summing of signals suited to eliminating a direct offset created during amplification of the HF signals.

A sensor assembly includes a sensor generating a sensor signal, an output unit and a condition unit receiving the sensor signal output from the sensor, and a test line connected to the sensor and the condition unit. The output unit outputs a signal output representative of a state detected by the sensor. The condition unit outputs a condition output representative of a condition of the sensor. The test line is bidirectional and outputs the condition output.